Centrifuging apparatus



Patented June 9, 1936 UNITED sTATEs PATENT orties 2 Claims.

This invention relates to centrifuging apparatus and is particularly devised for the purpose of aiding in the analysis of air or other gaseous bodies for the purpose of obtaining a quantitative analysisof the bacterial content of such air or gas.

Generally speaking, the invention embraces a centrifuging apparatus having a central air intake tube around which is revolved a tubular receptable containing a collecting medium, such for example as a cultural medium, which if in 4a fluid state, under the action of centrifugal force, builds up into a thin film on the inside wall of the tubular receptacle and over which the air admitted by the intake tube passes to the outlet, the bacterial or similar solid particles being centrifugally expelled from the column of air against the interior surface of the container lining before the air escapes. For convenience, the circulation of air through the intake tube and through the film receptacle is effected by providing the revolving outlet head with projecting vanes which act as a centrifugal fan or pump to draw the air through the intake tube and the film receptacle.

These and other features of the invention will be particularly described in the following specification and will be defined in claims annexed.

In the accompanying drawing I have illusltrated a simple and convenient apparatus embodying the principles of this invention, in which Fig. l is avertical central section of the cen-` trifuging apparatus connected at its bottom with a rotating motor or driving means.

Fig. 2 is a plan view, partly in section, on the section-indicating lines 2 2 of Fig. '1.

In the practice of this invention according to the specific form illustrated in the drawing, I provide .a base ring I having at its rear a vertical socket I@L for the reception of an upright rod or standard 2, on which is mounted a projecting supporting bracket 3 which is adjustably mountable at different levels on the standard 2 by means of the supporting nut 4, which carries a set screw for clamping it to any desired elevation on the standard.

The air tube bracket 3 at its outer end is provided with a central Vertical bore coaxially aligned with the driving shaft I6 of the underneath motor. The bracket is split at its outer end, as shown at 3a, and in the bore is inserted a gasket or bushing 5 of compressible material which firmly grips the exterior of an inserted air intake tube 6, the jaws 3a being clamped tightly by means of the clamping screw 3b. On the top of the air intake tube or duct 6 is mounted a calibrating intake nozzle l, that is, a nozzle whose central bore or passage is dimensioned to admit a predetermined quantity of air at uniform speed of rotation of the apparatus that is definitely known, so that the quantity of air passing through the intake at the normal speed of the apparatus in a given unit of time is definitely measured, since in bacterial analysis it is in most cases desirable to know the volume of air analyzed as well as the bacterial count.

A short distance below the suspension bracket 3 is secured around the intake tube 6 a bearing supporting collar 8, which carries a self-aligning anti-friction bearing II) which fitsvinto the upper end of the centrifuge head 9 and is protected by a circular cover I I secured to the upper end of the head.

The revolving head comprises upper and lower annular members 9, 9b having, respectively, radially projecting annular flanges 9a and 9C which are integrally united by means of vertical webs 9d which form the vanes or wings that act as a centrifugal fan to expel the air from the interior of the head, which is supplied to it from the intake tube 6. The head 9 is also provided with an inner hub or Yspider Se centrally bored to receive a tube I2, which is concentric with the air intake tube 6, which latter projects through to the lower end of the tube I2 and has a flared discharge end as shown at I5EL to nearly close the lower end of the tube I2 without actually coming in contact therewith inasmuch as the tube I2 rotates with the head, while the tube 6 is fixed or stationary. y

Fitted inside the lower member 9b of the centrifuge head is an outside tubular member i3, which forms a hollow drive shaft connection for rotating the centrifuge. There is sufficient annular space between the tube I2 and the hollow shaft I3 to permit the insertion of a receptacle or test tube2|l which carries in its bottom a small supply of iiuid which in bacterial analysis has the character of a cultural medium.

In its lower end the tubular casing or shaft I3 is releasably attached by means of clamping screws I5 to the driving head I4, which is itself secured to the projecting upper end of the spindle I6 of a driving motor M, which may be mechanically or electrically driven according to circumstances. In a recess formed in the top of the driving head I4 is secured an elastic cushion or pad I9 upon which the test tube or receptacle 2|] rests.

By releasing the clamping screws I5 carried by the head I4 the centrifuge may be raised on the standard 2 sufciently to permit the insertion of a test tube containing the fluid cultural medium with the bottom of the test tube resting on the cushion of pad I9. The test tube externally is very near the internal diameter of the casing or shaft I3, but need not ordinarily be attached thereto. After the insertion of the test tube the casing or shaft I3 is again coupled or clamped t0 the driving head I4 and upon the starting of the motor the fluid in the bottom of the receptacle under the influence of centrifugal force builds up into an annular lm on the inside of the wall of the receptacle, as indicated in dotted lines, thus exposing a hollow annular lm to contact with the air which, by means of the fan vanes 9d, is drawn down through the Calibrating nozzle I and thence upwardly between the tube I2 and the lrn of liquid until it escapes through the openings between the vanes. By reason of the revolution of the film itself on the outside of the column of air and of the tube I2 bounding the inside of the column of air, the column of air is also revolved as it moves upward and, owing to centrifugal force, the minute solid particles, such as bacteria or the like, are expelled against the liquid to which they adhere and which acts as a carrier for the accumulation of these minute bodies which it collects.

It will therefore be seen that the revolving of the centrifuge at normal speed not only builds up through centrifugal force an annular lm of liquid, but also draws in at a constant rate a known or ascertainable quantity of air from which the bacteria are expelled against the surrounding lm which retains them for cultural development and counting.

The bracket .'-i is splined to the rod 2, as shown at 3C, in order to prevent rotative displacement while permitting the bracket to slide upward for the insertion or removal of the test tube from the centrifuge.

While I have described the above apparatus as effective for the purpose of separating bacteria from a body of air, nevertheless it-will be understood that I do not confine myself to the use of the apparatus for such purpose, although it will be found that an apparatus built according to the above described principles is very effective in carrying out this new method'of bacterial analysis of air of which I am the inventor and which forms the subject matter of a companion application.

In making bacterial analysis of air the collecting is preferably formed centrifugally out of a gelazinous cultural substance, which at normal temperature is a jelly-like mass but which becomes liquid when hot, such for example as the well known medium; but in other analyses of air a collector sheet of celluloid or other suitable material may be inserted as a removable lining for the container and this has the advantage of ready removal from the revolving or centrifugal container so that the centrifugally extracted particles distributed over its surface may be easily subjected to microscopic or other examination and testing or counting after the lining has been removed. When the agar or like compound is used for the collecting medium or film, as above de scribed, it is unnecessary to remove it from the glass test tube because the cultural development can be seen through the transparent wall of the test tube or container and the count of cultural centers can be easily made from the outside, but this form of collector is not so well adapted t0 microscopic or chemical analysis of the particles and for such and similar purposes it is preferred to use a removable lining film inside the centrifugal container by reason of the greater accessibility alforded. Indeed, the test tube itself without any lining could be used as a collector of the centrifugally extracted particles since those particles are expelled with suflicient force at high speed to remain in xed position on the inside surface of the container, and bacteria so deposited could be treated later with a cultural medium to cause their development for further study. It will therefore be understood that the term collector is used herein to apply equally to the receptacle or container whether it be provided with a lining film or not, and whether such lining lm be formed by centrifugal action as above described or be formed by an insertable and removable sheet or nlm of material, so long as there is provided a collecting surface directly exposed to the moving column of air and serving as a means for collecting or retaining the particles centrifugally expelled upon it from the air. Since this arrangement provides for the lengthwise flow of a thin column of air, which receives its revolving motion from the revolving container, it will be seen that there will be an acceleration of revolution of the air as it moves toward the outlet end of the container-collector, thus causing a selective distribution of the particles along successive areas of the collector, the heavier particles being expelled first and the progressively lighter particles being deposited in order of their mass.

What I claim is:

l. An apparatus for air analysis embracing a supporting standard, a laterally projecting bracket slidably mounted thereon, a vertical air intake tube secured in said bracket for support, a bearing head carrying an exhaust fan revolubly mounted around said tube, a tubular casing having its upper end seated in said bearing head, a driving element connected with said casing, said air intake tube projecting down inside said tubular casing, an intermediate tube secured in said head and extending downward between said casing and said air intake tube and a removable liquid receptacle inserted between the casing and said intermediate tube.

2. An apparatus for air analysis embracing an upright standard, a laterally extending bracket projecting from said standard, an air intake tube mounted in said standard to 'project downwardly therefrom, a radial bearing mounted on said air tube below the bracket, a'revoluble head mounted on said bearing concentrically of said air tube, said head being provided with vanes for producing circulation of air and having concentric spaced bored recesses for receiving concentric tubes arranged concentrically around said air intake tube and providing an annular space for the reception of a tubular film container, a supporting and driving element detachably secured to the outside tube and forming a bottom support for a liquid container inserted between the two spaced concentric tubes.

WILLIAM F. WELLS. 

